Metal-oxide semiconductor field effect transistors (MOSFETs) are voltage-controlled power devices that are capable of handling large current flow. Typically, MOSFETS are used in high-speed switching applications and integrated circuits (ICs). For example, a digital power module (DPM) for an automotive vehicle may include one or more power MOSFETs for solid-state power switching. Vehicle body control functions and power distribution functions may be integrated on a vehicle DPM. These functions include, but are not limited to, interior and exterior lighting, windshield wipers, horn, air conditioning, clutch, fuel pump, starter relay, blower, system diagnostics, and/or smart fusing. MOSFETS may provide the smart fusing and/or other functions in the DPM.
A circuit or device that includes a MOSFET may include current overload, short circuit, and/or over temperature protection elements. For example, a circuit may include a current sensor and/or a temperature sensor to detect when a MOSFET is exposed to one or more of the above conditions.
Referring now to FIG. 1, an exemplary MOSFET circuit 10 includes a smart or sense MOSFET 12, a control circuit 14, a gate resistor 16, and a current detection resistor 18. The MOSFET 12 includes at least a gate terminal 20, a source terminal 22, a drain terminal 24, and a current detection terminal 26. The gate terminal 20 is connected to an input voltage 28 through the gate resistor 16. The control circuit 14 senses a current through the current detection resistor 18. The current through the current detection resistor 18 is indicative of a current through the MOSFET 12. Therefore, the control circuit 14 determines the current through the MOSFET 12. For example, the control circuit 14 may determine when the current through the MOSFET 12 exceeds a particular threshold.
In certain implementations, the MOSFET 12 may include TEM (temperature) MOSFET functions. A TEM MOSFET includes one or more temperature detection terminals (not shown). The temperature detection terminals output a signal that is indicative of a temperature of the MOSFET 12. In this manner, the control circuit 14 may determine when the temperature of the MOSFET 12 exceeds a particular threshold.
Therefore, a MOSFET circuit according to the above embodiments relies on smart, sense, and/or TEM MOSFETs for current overload and/or over temperature protection. Smart, sense, and TEM MOSFETs require additional terminals to provide the current/temperature sensing functions, thereby increasing package size and cost. Further, the additional terminals reduce space available for bonding wires. Alternatively, a MOSFET circuit may include a power shunt resistor to sense a load current. However, in large current applications, the shunt resistor may generate significant heat, which is undesirable.